To improve the energy dissipation efficiency and optimize the geometric parameters of a new type of butterfly-shaped steel plate damper, the calculation formulas for the initial stiffness and yield capacity of the new damper were firstly derived. Then, quasi-static tests were conducted on 8 damper specimens to comparatively investigate the failure modes, mechanical parameters, and hysteresis performance. Finally, through numerical simulation analysis of 67 models, the influence of parameters such as the width ratio a/b and height thickness ratio H/t of the energy dissipating ribs, number of energy dissipation ribs n, and number of steel plates N on the mechanical performance of the damper was explored. The results show that the mechanical performance of the new damper is stable with a plump hysteretic curve. The ultimate drift of the damper is greater than 10%, and the maximum equivalent viscous damping ratio exceeds 0.4. The mechanical performance of the damper is proportional to the number of energy dissipation ribs n and the number of steel plates N, which is convenient for standardized design. The initial stiffness, yield strength, and equivalent yield displacement of the damper can well be predicted by theoretical analysis, and the average calculation errors of the theoretical formulas are 14.0%, 8.4% and -10.9%, respectively. By designing the size of the energy dissipation ribs reasonably, the deformation state of full-section yielding can be achieved, resulting in a maximum energy dissipation per unit steel volume of 0.217 J/mm³. When the geometric parameters of the energy dissipation ribs satisfy the requirements of a/b=0.25-0.50 and H/t=20-30, the optimal energy dissipation economy of the new damper can be realized.